Periodic assemblies of materials have been shown to have unique and useful properties for microwave and optics applications. Examples of these are the photonic and microwave band gap structures, the left handed materials (LHM), and other related periodic assemblies. Such periodic media have allowed for several practical microwave components such as delay lines, couplers, and antennas.
In addition to band gap structures, other periodic structures offer unique and extraordinary properties. Among them, the magnetic photonic crystals (MPC) and their related “cousins” degenerate band edge (DBE) structures have been shown to lead to significant wave slow down and amplitude increase within a small region. These crystals have therefore been found very attractive for miniature and highly sensitive antennas and possibly miniature microwave devices. However, their anisotropic nature makes their fabrication extremely challenging and costly. Thus, there is a need to be able to emulate the MPC, DBE, and other electromagnetic properties and extraordinary modes as well as wave dispersion in such media using printed circuit technology, which would provide a significant step in making low cost, high performance devices based on MPC and DBE modes.
One exemplary embodiment of the present invention is novel coupled microstrip lines which may, for example, emulate propagation through an anisotropic medium such as MPC or DBE crystal. For example, a coupled microstrip line geometry may mimic the layered anisotropic medium making-up DBE or MPC crystals. In particular, one exemplary embodiment of the present invention may be comprised of coupled and uncoupled microstrip transmission line (TL) segments whose scattering parameter matrix (when cascaded) may form a periodic printed circuit that is adapted to deliver the band diagram of (or equivalently wave dispersion in) DBE or MPC crystals. Although some exemplary embodiments of the present invention may be particularly useful for MPC or DBE modes, it should be recognized that other extraordinary modes and electromagnetic properties may be achieved in various embodiments of the present invention.
In one exemplary embodiment, microstrip transmission line structures for a new class of photonic crystals may emulate degenerate band edge (DBE) and frozen mode behaviors in magnetic photonic crystals (MPC). For example, a microstrip line model may be formed from at least a pair of coupled and uncoupled lines adapted to emulate wave propagation within a bulk anisotropic layered medium. Wave dispersion within such periodic microstrip structures may support DBE and MPC modes for specific geometrical designs that can, for example, be readily manufactured using standard RF printed circuit techniques. Furthermore, in some exemplary embodiments of the present invention, manufacturing the printings on a ferrite substrate may allow for the realization of frozen modes as in MPC assemblies.
An exemplary embodiment of the present invention is the first time that microwave transmission line components may be used to emulate the extraordinary propagation phemomena encountered in periodic assemblies of bulk anisotropic dielectric and gyromagnetic ferrite materials. Further, the simplicity of an exemplary embodiment of printed microwave transmission lines together with mature circuit optimization tools allows for generating extremely fast and efficient designs of metamaterials displaying the aforementioned extraordinary modes as well as other unique electromagnetic properties, such as negative refraction index. Other benefits are also possible. An exemplary embodiment of a coupled transmission line layout can also be manufactured using solid state coupled optical fibers/channels and make use of gyroelectric and gyromagnetic behaviour of semiconductors to replace ferromagnetic substrates, thereby allowing for the realization of guided frozen light modes.
In addition to the novel features and advantages mentioned above, other benefits will be readily apparent from the following descriptions of the drawings and exemplary embodiments.